Dual injector solvent elution and focussing technique for the on-line analysis of solid-phase extraction cartridges in HPLC |
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Authors: | D R Rodier J W Birks |
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Institution: | (1) Department of Chemistry and Biochemistry and Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, 80309-0216 Boulder, CO, USA |
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Abstract: | Summary A new dual injector solvent focussing and elution technique developed for high-performance liquid chromatography (HPLC) greatly
improves chromatographic efficiency for the on-line analysis of C18 solid-phase extraction (SPE) cartridges. Solutions containing three benzene homologs were used to characterize the dual injector
analysis technique and to compare the chromatographic efficiency of this method with conventional SPE analysis methods. Sampling
was performed off-line using a glass precolumn cartridge (3 mm i.d. × 30 mm) packed with 15–35 μm C18 silica. On-line cartridge analysis was achieved with two injection valves in either serial or parallel configuration. The
injection loop of the first valve contains the eluting solvent, and the cartridge holder is connected in place of the injection
loop of the second valve. When an injection is made, both valves are turned to the inject position, and the solvent plug is
forced through the cartridge, focussing the analyte at the solvent front as it elutes the cartridge. Solvent focussing at
the head of the column, resulting from preconditioning of the column with a small plug of water during injection, further
minimizes the variance of the injection plug and improves the chromatographic efficiency. The technique has potential applications
to environmental and biological fluid analysis where analyte preconcentration and resolution from the sample matrix components
may be difficult with current SPE methods. |
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Keywords: | Column liquid chromatography Sample preconcentration Solid-phase extraction Solvent focussing Injection techniques |
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